Buffers¶
Usage
use Buffers;
or
import Buffers;
Support for buffers - regions of memory without a particular interpretation.
This module provides byteBuffer
and buffer
types which
can be used to manage memory regions.
These types should be safe to use in a multi-locale context. These types should free their memory after the last user of that memory goes out of scope. They are currently reference counted but that may not always be the case.
Bytes Type¶
A byteBuffer
is a contiguous memory region - really a data structure
containing a pointer, length, and also the information necessary to free the
memory region when it is no longer used.
Buffers¶
A buffer
consists of a sequence of views into byteBuffer
objects. A byteBuffer
object might be shared by several
buffer
objects.
It is efficient to go to a particular offset in a buffer, and to push or pop
bytes objects from the beginning or end of a buffer.
-
record
byteBuffer
¶ This type represents a contiguous sequence of bytes. This sequence of bytes is represented with a C pointer and length and is currently reference counted. Note that this record contains private fields in addition to the home field.
-
var
home
: locale¶ The home locale storing the data
-
var
-
proc
byteBuffer.
init
()¶ Initialize an empty bytes object
-
proc
byteBuffer.
init
(len: int(64), out error: syserr) Initialize a bytes object by allocating zero-filled memory.
Arguments: - len – the number of bytes to allocate
- error – (optional) capture an error that was encountered instead of halting on error
-
proc
byteBuffer.
ptr
(): c_void_ptr¶ Note
The pointer returned by this method is only valid for the lifetime of the byteBuffer object and will be invalid if this memory is freed.
Returns: a c_void_ptr to the internal byte array
-
proc
byteBuffer.
len
: int(64)¶ Returns: the number of bytes stored in a byteBuffer
object
-
record
buffer_iterator
¶ This type represents a particular location with a buffer. Use buffer methods like
buffer.start
andbuffer.advance
to create and manipulatebuffer_iterator
s. Note that this record contains private fields in addition to the home field.-
var
home
: locale¶ The home locale storing the data
-
var
-
record
buffer_range
¶ A region within a buffer (indicated by two
buffer_iterator
s )-
var
start
: buffer_iterator¶
-
var
end
: buffer_iterator¶
-
var
-
proc
buffer_range.
len
: int(64)¶ Returns: the number of bytes stored in a buffer_range
-
record
buffer
¶ A buffer which can contain multiple memory regions (that is, multiple regions of
byteBuffer
objects). Note that this record contains private fields in addition to the home field.-
var
home
: locale¶ The home locale storing the data
-
var
-
proc
buffer.
init
(out error: syserr)¶ Create an empty buffer.
Arguments: error – (optional) capture an error that was encountered instead of halting on error
-
proc
buffer.
flatten
(range: buffer_range) throws¶ Flatten a buffer. Create a new
byteBuffer
object and copy the buffer into it. This function should work even if buffer is remote.Arguments: range – the region of the buffer to copy, for example buffer.all() Returns: a newly initialized bytes object on the current locale
-
proc
buffer.
append
(b: byteBuffer, skip_bytes: int(64) = 0, len_bytes: int(64) = b.len) throws¶ Append a
byteBuffer
object to abuffer
. This function might store the passed bytes object by reference instead of copying it. The current implementation will always do so and will always increase the reference count of the bytes object. The version of this function called without the error argument will halt if an error is encountered.Arguments: - b – the
byteBuffer
object to append - skip_bytes – how many bytes at the front of b to skip
- len_bytes – how many bytes to append to the buffer
- b – the
-
proc
buffer.
append
(buf: buffer, part: buffer_range = AppendExpr.Call08) throws Append a
buffer
object to abuffer
. This function might store a pointers to the bytes objects contained in buf instead of copying them. If that happens, the current implementation will increase their reference counts. The version of this function called without the error argument will halt if an error is encountered.Arguments: - buf – the
buffer
object to append - part – a
buffer_range
indicating which section of the buffer to copy. Defaults to all of the buffer.
- buf – the
-
proc
buffer.
prepend
(b: byteBuffer, skip_bytes: int(64) = 0, len_bytes: int(64) = b.len) throws¶ Prepend a
byteBuffer
object to abuffer
. This function might store the passed bytes object by reference instead of copying it. The current implementation will always do so and will always increase the reference count of the bytes object. The version of this function called without the error argument will halt if an error is encountered.Arguments: - b – the
byteBuffer
object to prepend - skip_bytes – how many bytes at the front of b to skip
- len_bytes – how many bytes to append to the buffer
- b – the
-
proc
buffer.
start
(): buffer_iterator¶ Returns: a buffer_iterator
to the start of a buffer
-
proc
buffer.
end
(): buffer_iterator¶ Returns: a buffer_iterator
to the end of a buffer
-
proc
buffer.
all
(): buffer_range¶ Returns: a buffer_range
for the entirety of a buffer
-
proc
buffer.
next_part
(ref it: buffer_iterator)¶ Advance a
buffer_iterator
to the next contiguous memory region stored thereinArguments: it – the buffer iterator to advance
-
proc
buffer.
prev_part
(ref it: buffer_iterator)¶ Advance a
buffer_iterator
to the previous contiguous memory region stored thereinArguments: it – the buffer iterator to advance
-
proc
buffer.
advance
(ref it: buffer_iterator, amount: int(64))¶ Advance a
buffer_iterator
by a particular number of bytes.Arguments: - it – the buffer iterator to advance
- amount – the number of bytes to advance
-
proc
buffer.
copyout
(it: buffer_iterator, out value: ?T): buffer_iterator throws¶ Read a basic type (integral or floating point value) or string from a buffer. For basic types, this method reads the value by copying from memory - so it reads a binary value in native endianness. For strings, this method reads a string encoded as the string length (as int) followed by that number of bytes (as uint(8)).
Arguments: - it – a
buffer_iterator
where reading will start - value – a basic type or string
Returns: a buffer iterator storing the position immediately after the read value.
- it – a
-
proc
buffer.
copyin
(it: buffer_iterator, value: ?T): buffer_iterator throws¶ Write a basic type (integral or floating point value) or string to a buffer. For basic types, this method writes the value by copying to memory - so it writes a binary value in native endianness. For strings, this method writes a string encoded as the string length (as int) followed by that number of bytes (as uint(8)).
Arguments: - it – a
buffer_iterator
where reading will start - value – a basic type or string
Returns: a buffer iterator storing the position immediately after the written value.
- it – a